pgp-OLD-lines.md

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Lines and Networks

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Linear Referencing/Line Handling

Select every Nth point from a LineString

https://stackoverflow.com/questions/60319473/postgis-how-do-i-select-every-second-point-from-linestring

Extrapolate Lines

https://gis.stackexchange.com/questions/33055/extrapolating-a-line-in-postgis

ST_LineInterpolatePoint should be enhanced to allow fractions outside [0,1].

Extend a LineString to the boundary of a polygon

https://gis.stackexchange.com/questions/345463/how-can-i-extend-a-linestring-to-the-edge-of-an-enclosing-polygon-in-postgis

Ideas A function ST_LineExtract(line, index1, index2) to extract a portion of a LineString between two indices

Extract Line Segments

https://gis.stackexchange.com/questions/174472/in-postgis-how-to-split-linestrings-into-their-individual-segments

PostGIS Idea

Create an ST_DumpSegments to do this.

Networks

Find Shortest Path through linear network

Input Parameters: linear network MultiLineString, start point, end point

Start and End point could be snapped to nearest endpoints if not already in network Maybe also function to snap a network?

“Longest Shortest Path” - perhaps: construct Convex Hull, take longest diameter, find shortest path between those points

https://gis.stackexchange.com/questions/295199/how-do-i-select-the-longest-connected-lines-from-postgis-st-approximatemedialaxi

Routing / Pathfinding

Seaway Distances & Routes

https://www.ausvet.com.au/seaway-distances-with-postgresql/

Temporal Trajectories

Find Coincident Paths

https://www.cybertec-postgresql.com/en/intersecting-gps-tracks-to-identify-infected-individuals/

Remove Stationary Points

https://gis.stackexchange.com/questions/290243/remove-points-where-user-was-stationary